WO1993023348A1 - Method of ceramic coating - Google Patents

Method of ceramic coating Download PDF

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Publication number
WO1993023348A1
WO1993023348A1 PCT/GB1993/000999 GB9300999W WO9323348A1 WO 1993023348 A1 WO1993023348 A1 WO 1993023348A1 GB 9300999 W GB9300999 W GB 9300999W WO 9323348 A1 WO9323348 A1 WO 9323348A1
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WO
WIPO (PCT)
Prior art keywords
coating
sol
ceramic
article
backbone
Prior art date
Application number
PCT/GB1993/000999
Other languages
French (fr)
Inventor
Ronald Jones
Original Assignee
S.D. Investments Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by S.D. Investments Limited filed Critical S.D. Investments Limited
Publication of WO1993023348A1 publication Critical patent/WO1993023348A1/en

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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/60—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only artificial stone
    • C04B41/61—Coating or impregnation
    • C04B41/62—Coating or impregnation with organic materials
    • C04B41/64—Compounds having one or more carbon-to-metal of carbon-to-silicon linkages
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
    • C04B41/4505—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements characterised by the method of application
    • C04B41/4535—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements characterised by the method of application applied as a solution, emulsion, dispersion or suspension
    • C04B41/4537—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements characterised by the method of application applied as a solution, emulsion, dispersion or suspension by the sol-gel process
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
    • C04B41/46—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with organic materials
    • C04B41/49—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes
    • C04B41/4905—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes containing silicon
    • C04B41/4922—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes containing silicon applied to the substrate as monomers, i.e. as organosilanes RnSiX4-n, e.g. alkyltrialkoxysilane, dialkyldialkoxysilane
    • C04B41/4944—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes containing silicon applied to the substrate as monomers, i.e. as organosilanes RnSiX4-n, e.g. alkyltrialkoxysilane, dialkyldialkoxysilane containing atoms other than carbon, hydrogen, oxygen, silicon, alkali metals or halogens, e.g. N-silyldisilazane: Image
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
    • C04B41/46—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with organic materials
    • C04B41/49—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes
    • C04B41/4905—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes containing silicon
    • C04B41/495—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes containing silicon applied to the substrate as oligomers or polymers
    • C04B41/4961—Polyorganosiloxanes, i.e. polymers with a Si-O-Si-O-chain; "silicones"
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/60—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only artificial stone
    • C04B41/61—Coating or impregnation
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D183/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Coating compositions based on derivatives of such polymers
    • C09D183/04—Polysiloxanes
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/02—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition
    • C23C18/12—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material
    • C23C18/1204—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material inorganic material, e.g. non-oxide and non-metallic such as sulfides, nitrides based compounds
    • C23C18/1208—Oxides, e.g. ceramics
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/02—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition
    • C23C18/12—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material
    • C23C18/1204—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material inorganic material, e.g. non-oxide and non-metallic such as sulfides, nitrides based compounds
    • C23C18/122—Inorganic polymers, e.g. silanes, polysilazanes, polysiloxanes
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/02—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition
    • C23C18/12—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material
    • C23C18/125—Process of deposition of the inorganic material
    • C23C18/1254—Sol or sol-gel processing
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • C04B2111/23—Acid resistance, e.g. against acid air or rain

Definitions

  • the present invention relates to methods of coating and compositions for use in such methods-
  • the invention relates to protective coatings for panels which may be used architecturally, either interior or exterior of buildings and other structures.
  • the panels need to be corrosion resistant to acid and alkali, erosion resistant to airborne dust, scratch resistant, resistant to discolouration by ultraviolet light, capable of withstanding most normal weather conditions, capable, of freeze/thaw cycling and capable of withstanding graffiti removal cleaning agents.
  • a method of protecting a surface of an article comprising the steps of preparing a substantially colloidal sol containing ceramic material, coating said sol onto areas of said surface which require protection or for which protection is advisable, and curing said coated article.
  • the object of the curing step is to cause the ceramic material to harden into a protective coating, and this may be achieved by a number of alternative methods such as firing at a temperature of between 50°C and 350°C, or curing by exposure to I.R or U.V radiation.
  • the preferred method is thermal curing by firing' at a temperature of between 100°C and 300°C, the most preferred temperature range being in the region of 150°C - 250°C, ideally in the region of less than 200°C. This comparatively low firing temperature enables the ceramic material to harden into a protective coating but does not damage or degrade the material of the article or any surface coating thereon.
  • the ceramic material may be an organically substituted silane or siloxane.
  • other elements such as aluminium, zirconium or titanium may be included in the composition or in the backbone of the siloxane.
  • the sol may be a colloidal dispersion in an organic solvent such as isopropanol.
  • a coating which can produce a ceramic layer at a temperature low enough to allow it to be used on most materials, or even over paints already applied to boards whereby it gives additional weathering resistance.
  • a coating is applied as a colloidal dispersion in an organic solvent and this means that the particles are sufficiently small to have a large surface area to volume ratio and therefore, they can be cured by firing at a temperature as low as 150°C - 250°C.
  • the coatings are in fact produced by polymerising a ceramic backbone which is modified with various organic side groups. Other metal atoms may be incorporated into the ceramic backbone, if so desired.
  • the organic groups grafted onto the polymer make it possible to densify the coatings at a low temperature compared to that at which an unmodified ceramic coating would densify.
  • the other elements which may be incorporated into the backbone are aluminium, zirconium or titanium or other such metals.
  • the colloidal sol may be applied to the surface of the building panels or other article by such conventional techniques as spray, roller, curtain or dip coating.
  • the viscosity of the sol may be varied to suit the chosen application method.
  • the curing temperature range is generally between 50°C and 350°C and the time required for curing may very from 1 minute to 2 hours depending upon the formulation.
  • This solution is then sprayed onto the edges of the panel and the curing polymerisation brought about by heating in a stoving oven at 150°C for 30 minutes.
  • Panels have been subjected to accelerated weathering tests in a QUV weathero eter which exposes the sample to ultraviolet light for 3 hours then humidity for 3 hours and this cycle is repeated for 3000 hours.
  • the inorganic backbone polymer gives the panel its corrosion resistance and when modified with methyl groups excellent UV resistance.
  • Ceral bent edge coating which is essentially a polysiloxane resin containing aluminium oxide cross linkages, is prepared as two separate sols which need to be mixed together a minimum of 12 hours prior to application.
  • This formulation is prepared as follows:-
  • Sol A is prepared by dissolving 127.lOg of polymethylsilsiquioxane powder gradually into 150ml of isopropanol over 5-6 hours.
  • Sol B is prepared by mixing lOOg of aluminium sec butoxide with 500ml of ethyl acetoacetone, mixing slowly to prevent excessive temperature rise. Sol B is stirred continually for a minimum of 3 hours.
  • Sols A and B are then mixed together in the following ratio by weight:-
  • This coating solution can be applied by standard dipping, spray, and roller coating techniques. This coating has been applied to the bent edges of enamelled aluminium and stainless steel. It has provided protection against corrosion and helps prevent spalling of the enamel at the bend.
  • This coating is thermally cured at temperatures between 180°C and 210°C - the higher the curing temperature the harder the resultant coating.
  • Bent panels protected by this coating have been subjected to accelerated weathering testing in a QUV weatherometer which exposes panels to repeated 4 hour cycles of UVA & B and humidity/condensation. The testing has been carried out for 3000 hours with no obvious deterioration of the coating. Further improvements in the flexibility and UV resistance can be achieved by addition of coupling agents containing functionalities such as acryloxy, methacryloxy and vinyl. Examples of such coupling agents include the following:-
  • the solution can be used for dip coating, spraying or any suitable application technique.
  • This coating is more suitable for internal use since its UV ageing characteristics are not as good as the solution in Example 1 due to the presence of epoxy groups.
  • both the above boards were coated with the following formulation which gave excellent scratch resistance and enabled a wider range of graffiti removal solvents to be used without detriment to the painted surface.
  • the coating was for internal purposes since the UV resistance was poor.
  • Example 1 For external use and good chemical resistance to solvents the coating solution from Example 1 can be used but instead of adding lOg aluminium sec butoxide in 50mls ethyl aceto acetonate, lOOmls of acetoxy terminated polymethyl siloxane are added.
  • the salt environment can be simulated in salt spray chambers which are used to compare coatings for filiform corrosion. There are standard tests.
  • the ceramic polymer coating described below at 20 ⁇ m thickness decelerates this corrosion process by a factor of 4 compared to polyester clear lacquer at a thickness of 30 ⁇ m.
  • This coating has been applied to both chromated and unchromated surfaces of extruded window frames for exterior applications.
  • a suitable formulation for this is prepared as follows:
  • the coating is capable of operating to 300°C which is well in excess of the performance temperature of polyester epoxy and urethane coatings.
  • portioning board are extremely porous and contain materials which absorb humidity which prevents their use in areas such as swimming pools, kitchens, bathrooms and showers. It is possible to apply a surface coating to the board but in circumstances where there is for instance a suspended ceiling the edges and back face eventually absorb
  • Porous boards have been treated with the following formulation which helps to prevent moisture ingress into the material.
  • 400g phenyl triethoxy silane are mixed in 400mls of isopropanol and lOOmls of methanol.
  • This system also gives reasonable resistance to acid attack and can therefore be used on external porous surfaces of plaster and exposed to environmental pollution such as acid rain.
  • the coated articles are cured thermally, generally between 150°C and 200°C.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Structural Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • General Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Dispersion Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Paints Or Removers (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)

Abstract

A method of protecting a surface of an article comprising the steps of preparing a substantially colloidal sol containing ceramic material, coating said sol onto areas of said surface which require protection or for which protection is advisable, and curing said coated article.

Description

METHOD OF CERAMIC COATING
The present invention relates to methods of coating and compositions for use in such methods-
More particularly, but not exclusively, the invention relates to protective coatings for panels which may be used architecturally, either interior or exterior of buildings and other structures.
Particularly for exteriors, although in some cases, for interiors as well, the panels need to be corrosion resistant to acid and alkali, erosion resistant to airborne dust, scratch resistant, resistant to discolouration by ultraviolet light, capable of withstanding most normal weather conditions, capable, of freeze/thaw cycling and capable of withstanding graffiti removal cleaning agents.
It is known to provide panels which fulfil all of the above requirements reasonably well, but these use vitreous enamelled steel which is heavy and not always easy to use. Attempts have been made to find a lighter alternative to such materials. The problem is often that they may be lighter but they do not fulfil the above requirements. It is possible to produce a panel material which is protected by paints or lacquer coatings, which may be polyester, polyurethane or epoxy resins but these will not give the same life as an inorganic ceramic or glass coating such as vitreous enamel.
It is an object of the present invention to provide a ceramic protective coating, especially for a panel as described above. It is also an object of the present invention to provide a method of using the coating to protect panels and other articles.
According to the first aspect of the present invention there is provided a method of protecting a surface of an article comprising the steps of preparing a substantially colloidal sol containing ceramic material, coating said sol onto areas of said surface which require protection or for which protection is advisable, and curing said coated article.
The object of the curing step is to cause the ceramic material to harden into a protective coating, and this may be achieved by a number of alternative methods such as firing at a temperature of between 50°C and 350°C, or curing by exposure to I.R or U.V radiation.
The preferred method is thermal curing by firing' at a temperature of between 100°C and 300°C, the most preferred temperature range being in the region of 150°C - 250°C, ideally in the region of less than 200°C. This comparatively low firing temperature enables the ceramic material to harden into a protective coating but does not damage or degrade the material of the article or any surface coating thereon.
The ceramic material may be an organically substituted silane or siloxane. Optionally, other elements such as aluminium, zirconium or titanium may be included in the composition or in the backbone of the siloxane.
The sol may be a colloidal dispersion in an organic solvent such as isopropanol.
The invention will now be more particularly described.
It concerns a coating which can produce a ceramic layer at a temperature low enough to allow it to be used on most materials, or even over paints already applied to boards whereby it gives additional weathering resistance. A coating is applied as a colloidal dispersion in an organic solvent and this means that the particles are sufficiently small to have a large surface area to volume ratio and therefore, they can be cured by firing at a temperature as low as 150°C - 250°C. The coatings are in fact produced by polymerising a ceramic backbone which is modified with various organic side groups. Other metal atoms may be incorporated into the ceramic backbone, if so desired. The organic groups grafted onto the polymer make it possible to densify the coatings at a low temperature compared to that at which an unmodified ceramic coating would densify. The other elements which may be incorporated into the backbone are aluminium, zirconium or titanium or other such metals.
The colloidal sol may be applied to the surface of the building panels or other article by such conventional techniques as spray, roller, curtain or dip coating. The viscosity of the sol may be varied to suit the chosen application method.
The curing temperature range is generally between 50°C and 350°C and the time required for curing may very from 1 minute to 2 hours depending upon the formulation.
The invention will now be more particularly described with reference to the following non-limiting Examples, showing the use of various ceramic coatings applied to different products.
EXAMPLE 1
Ceral
This product has been designed for walling applications. It is a registered trade name of NGK (Japan) a true inorganic enamel made by a continuous operation and therefore produced as coil. The product has been used successfully in many internal applications and there is now a desire to produce exterior architectural panels from the material.
In order to make the panel rigid enough for this application it is desirable to bend edges to produce a flange. Once the enamel is bent through a small radius the enamel cracks exposing the metal surface underneath. This takes away the weathering resistance that had been created by an integral coat of enamel over the metal. It is now possible to coat this bent edge with a ceramic polymer which then protects the exposed edge and increases the weathering resistance back to the capability of the uncracked,enamel.
The formulation and method of preparation of this polymer is given below:
Typical formulation
500g polymethylsilsequioxane 500mls isopropanol Reflux for 1.5 hours
Cool then add:
10Og acetoxy terminated polymethyl siloxane lOg tetraethoxysilane 625mls propanol
The pH is adjusted to 4.8 then the solution refluxed for 3 hours. Finally lOg of aluminium sec butoxide and 50mls ethyl aceto acetone are added and the solution stirred for one hour.
This solution is then sprayed onto the edges of the panel and the curing polymerisation brought about by heating in a stoving oven at 150°C for 30 minutes.
Panels have been subjected to accelerated weathering tests in a QUV weathero eter which exposes the sample to ultraviolet light for 3 hours then humidity for 3 hours and this cycle is repeated for 3000 hours.
The inorganic backbone polymer gives the panel its corrosion resistance and when modified with methyl groups excellent UV resistance.
An alternative formulation for the Ceral bent edge coating, which is essentially a polysiloxane resin containing aluminium oxide cross linkages, is prepared as two separate sols which need to be mixed together a minimum of 12 hours prior to application. This formulation is prepared as follows:-
Sol A is prepared by dissolving 127.lOg of polymethylsilsiquioxane powder gradually into 150ml of isopropanol over 5-6 hours.
Sol B is prepared by mixing lOOg of aluminium sec butoxide with 500ml of ethyl acetoacetone, mixing slowly to prevent excessive temperature rise. Sol B is stirred continually for a minimum of 3 hours.
Sols A and B are then mixed together in the following ratio by weight:-
Sol A 16
Sol B 1
This coating solution can be applied by standard dipping, spray, and roller coating techniques. This coating has been applied to the bent edges of enamelled aluminium and stainless steel. It has provided protection against corrosion and helps prevent spalling of the enamel at the bend.
This coating is thermally cured at temperatures between 180°C and 210°C - the higher the curing temperature the harder the resultant coating.
Bent panels protected by this coating have been subjected to accelerated weathering testing in a QUV weatherometer which exposes panels to repeated 4 hour cycles of UVA & B and humidity/condensation. The testing has been carried out for 3000 hours with no obvious deterioration of the coating. Further improvements in the flexibility and UV resistance can be achieved by addition of coupling agents containing functionalities such as acryloxy, methacryloxy and vinyl. Examples of such coupling agents include the following:-
3 Acryloxypropyl methyldichlorosilane
3 Acryloxypropyl trimethoxysilane
3 (Methacryloxy) propyl triethoxysilane
Vinyl trimethoxysilane
Vinyl triethoxysilane
These agents are added to Sol A prior to mixing with Sol B.
EXAMPLE 2
Porous Cladding Boards
There are many cladding boards used as partitioning generally for internal use. Many of the boards exhibit some degree of fire protection. The problem with such board is often water or liquid absorption from accidental spillage. It is possible to modify the ceramic backbone of the polymer with organic phenyl groups which exhibit a hydrophobic tendency. This coating solution is more suitable for porous surfaces as a barrier coating and not suitable for smooth surfaces such as glass or metal.
A typical formulation is given below:
lOOOmls methyl trimethoxy silane lOOmlε isopropanol
40g acetoxy terminated polydimethoxy silane
80g 2(3-4) epoxy cyclohexyl) ethy trimethoxy silane
3mls glacial acetic acid
These ingredients are refluxed for 3 hours cooled and then 300mls of colloidal silica sol (50% weight of solids) are added and stirred.
The solution can be used for dip coating, spraying or any suitable application technique. This coating is more suitable for internal use since its UV ageing characteristics are not as good as the solution in Example 1 due to the presence of epoxy groups.
EXAMPLE 3
Mirral and Glassal* fRTM)
These are two wall cladding boards that can be used either internally or externally. In public places the problem is often removal of graffiti. Graffiti removal solvents can be harsh to painted surfaces and can dull gloss finish, discolour the paint or even strip the paint.
For internal use both the above boards were coated with the following formulation which gave excellent scratch resistance and enabled a wider range of graffiti removal solvents to be used without detriment to the painted surface. The coating was for internal purposes since the UV resistance was poor.
125g 2(3,4, epoxy cyclohexyl ethyl trimethoxy silane
50mls toluene
50mls ethanol are refluxed together for one hour.
71.8 g of α amino propyl trimethoxy silane and then 79.9g of aluminium sec-butoxide in 25mls of ethyl aceto acetate are added and the mixture refluxed again for 1 hour.
Finally the reaction is catalysed by the addition of 3mls of glacial acetic acid.
For external use and good chemical resistance to solvents the coating solution from Example 1 can be used but instead of adding lOg aluminium sec butoxide in 50mls ethyl aceto acetonate, lOOmls of acetoxy terminated polymethyl siloxane are added.
EXAMPLE 4
Aluminium Extrusions
Aluminium and many of its alloys corrode easily in a salt environment. If the surface is coated with a polymer such as polyester resin, epoxy resin or polyurethane resin which is an organic system and the coating becomes scratched a form of corrosion takes place where the corrosion grows in fingers between the coating and the metal. The phenomenon is called filiform corrosion. The salt environment can be simulated in salt spray chambers which are used to compare coatings for filiform corrosion. There are standard tests. The ceramic polymer coating described below at 20μm thickness decelerates this corrosion process by a factor of 4 compared to polyester clear lacquer at a thickness of 30μm.
This coating has been applied to both chromated and unchromated surfaces of extruded window frames for exterior applications.
A suitable formulation for this is prepared as follows:
500g of methyl trimethoxy silane
400g of (3 glycidoxy propyl) trimethyoxy silane in
400g propanol and 100 is methanol are refluxed together for two hours.
3g of tin octoate are added and the solution refluxed one hour. Finally 3g of acetic acid are added whilst stirring. The curing temperature for this coating is
150°C for 30 minutes but the coating is capable of operating to 300°C which is well in excess of the performance temperature of polyester epoxy and urethane coatings.
EXAMPLE 5
Porous Portioning Board
Some forms of portioning board are extremely porous and contain materials which absorb humidity which prevents their use in areas such as swimming pools, kitchens, bathrooms and showers. It is possible to apply a surface coating to the board but in circumstances where there is for instance a suspended ceiling the edges and back face eventually absorb
moisture. Porous boards have been treated with the following formulation which helps to prevent moisture ingress into the material.
500g ethy trimethoxy silane
400g phenyl triethoxy silane are mixed in 400mls of isopropanol and lOOmls of methanol.
After thorough mixing, 300mls of sodium silicate solution are mixed in.
This system also gives reasonable resistance to acid attack and can therefore be used on external porous surfaces of plaster and exposed to environmental pollution such as acid rain.
In Examples 2, 3 and 5, the coated articles are cured thermally, generally between 150°C and 200°C.

Claims

1. A method of protecting a surface of an article comprising the steps of preparing a substantially colloidal sol containing ceramic material, coating said sol onto areas of said surface which require protection or for which protection is advisable, and curing said coated article.
2. A method according to Claim 1 wherein said curing step comprises firing at a temperature of between 50°C and 350°C.
*3. A method according to Claim 2 wherein the coated article is fired at a temperature of between 150°C and 200°C.
4. A method according to Claim 1 wherein the curing step comprises exposure to I.R or U.V radiation.
5. A method according to any of the preceding claims wherein the ceramic material is an organically substituted silane or siloxane.
6. A method according to Claim 5 wherein at least one other element such as aluminium, zirconium or titanium is included in the composition or in the backbone of the silane/siloxane.
7. A method according to any of the preceding claims wherein the sol is a colloidal dispersion in an organic solvent such as isopropanol.
8. A method according to any of the preceding claims wherein the coating is produced by polymerising a ceramic backbone which is modified with various organic side groups.
9. A method according to Claim 8 wherein other metal atoms such as aluminium, zirconium or titanium are incorporated into the ceramic backbone.
10. A method according to any of the preceding claims wherein the colloidal sol is applied to the surface of the building panels or other article by such conventional techniques as spray, roller, curtain or dip coating.
11. A method according to Claim 10 wherein the viscosity of the sol may be varied to suit the chosen application method.
12. A building panel treated by the method of any of the preceding claims.
PCT/GB1993/000999 1992-05-15 1993-05-14 Method of ceramic coating WO1993023348A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9210476.9 1992-05-15
GB929210476A GB9210476D0 (en) 1992-05-15 1992-05-15 Method of ceramic coating

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Publication number Priority date Publication date Assignee Title
FR2731442A1 (en) * 1995-03-09 1996-09-13 Ugine Sa METHOD FOR REALIZING A COATING ON AN ELECTRIC STEEL SHEET AND OBTAINED
WO1997001599A1 (en) * 1995-06-28 1997-01-16 E.I. Du Pont De Nemours And Company Fluoropolymer nanocomposites
US5726247A (en) * 1996-06-14 1998-03-10 E. I. Du Pont De Nemours And Company Fluoropolymer nanocomposites
DE4401671B4 (en) * 1994-01-21 2006-05-04 Km Europa Metal Ag Process for reducing the solubility of copper ions from pipes of copper or copper alloys and copper pipe with reduced copper solubility

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FR2276363A1 (en) * 1974-06-25 1976-01-23 Dow Corning COMPOSITION OF PAINT BASED ON COLLOIDAL SILICA AND PARTIAL CONDENSATE OF A SILANOL
US4408009A (en) * 1982-02-17 1983-10-04 Union Carbide Corporation Co-condensates of alkyl silicates and alkoxy silanes
US4423096A (en) * 1982-11-03 1983-12-27 Nalco Chemical Company Method for protecting porous ceramic building materials exposed to weathering
EP0206717A2 (en) * 1985-06-17 1986-12-30 Nissan Chemical Industries Ltd. Coating compositions
EP0263428A2 (en) * 1986-10-03 1988-04-13 Ppg Industries, Inc. Organosiloxane/metal oxide coatings
EP0443760A2 (en) * 1990-02-22 1991-08-28 Dow Corning Corporation Precursor polymer for ceramic coatings
EP0479452A2 (en) * 1990-10-01 1992-04-08 Dow Corning Corporation Perhydrosiloxane copolymers and their use as coating materials

Patent Citations (7)

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Publication number Priority date Publication date Assignee Title
FR2276363A1 (en) * 1974-06-25 1976-01-23 Dow Corning COMPOSITION OF PAINT BASED ON COLLOIDAL SILICA AND PARTIAL CONDENSATE OF A SILANOL
US4408009A (en) * 1982-02-17 1983-10-04 Union Carbide Corporation Co-condensates of alkyl silicates and alkoxy silanes
US4423096A (en) * 1982-11-03 1983-12-27 Nalco Chemical Company Method for protecting porous ceramic building materials exposed to weathering
EP0206717A2 (en) * 1985-06-17 1986-12-30 Nissan Chemical Industries Ltd. Coating compositions
EP0263428A2 (en) * 1986-10-03 1988-04-13 Ppg Industries, Inc. Organosiloxane/metal oxide coatings
EP0443760A2 (en) * 1990-02-22 1991-08-28 Dow Corning Corporation Precursor polymer for ceramic coatings
EP0479452A2 (en) * 1990-10-01 1992-04-08 Dow Corning Corporation Perhydrosiloxane copolymers and their use as coating materials

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4401671B4 (en) * 1994-01-21 2006-05-04 Km Europa Metal Ag Process for reducing the solubility of copper ions from pipes of copper or copper alloys and copper pipe with reduced copper solubility
FR2731442A1 (en) * 1995-03-09 1996-09-13 Ugine Sa METHOD FOR REALIZING A COATING ON AN ELECTRIC STEEL SHEET AND OBTAINED
EP0735117A1 (en) * 1995-03-09 1996-10-02 USINOR SACILOR Société Anonyme Process for coating an electrical steel sheet and electrical sheet made by this method
WO1997001599A1 (en) * 1995-06-28 1997-01-16 E.I. Du Pont De Nemours And Company Fluoropolymer nanocomposites
US5726247A (en) * 1996-06-14 1998-03-10 E. I. Du Pont De Nemours And Company Fluoropolymer nanocomposites

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GB9210476D0 (en) 1992-07-01

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